1. Field of the Invention
The present invention relates to a method of detecting abnormality in a fuel cell.
2. Description of the Related Art
A fuel cell mounted in a fuel cell vehicle or the like comprises a stack formed by stacking a plurality of unit cells that are respectively formed by sandwiching a solid polymer electrolyte membrane comprising a solid polymer ion exchange membrane or the like between the anode and cathode, and interposing a pair of separators on the outside thereof. In each cell, a hydrogen gas duct that supplies hydrogen gas as the fuel gas, an air duct that supplies air that includes oxygen as an oxidizing agent, and a cooling liquid duct that supplies a coolant are provided. Below, the fuel gas and the oxidizing gas are abbreviated “reacting gases”. In the fuel cell, the hydrogen ions that are generated by the catalytic reaction at the anode migrate to the cathode by passing through the solid polymer catalyst membrane, and electricity is generated at the cathode due to an electro-chemical reaction with the oxygen. In addition, the heat generated during power generation is captured by a coolant in the coolant duct, and thereby the fuel cell is cooled.
In this fuel cell, as an electrolyte, this solid polymer electrolyte membrane has the function of transmitting the hydrogen ions and, as a barrier, the function of separating the hydrogen gas in the hydrogen gas duct and the oxidizing gas (air) in the air duct, and in addition, as a barrier, the separator has the function of respectively separating the hydrogen gas in the hydrogen gas duct, the oxidizing gas (air) in the air duct, and the coolant in the coolant duct. Therefore, if holes open in the solid polymer electrolyte membrane or the separators, the hydrogen in the hydrogen gas duct will leak into the air duct.
Because it is a flammable gas, when the hydrogen gas leaks into the air duct in this manner, the hydrogen gas is heated reacting with the oxygen in the air in the air passage, and there is a concern that this will be a detrimental influence on the fuel cell.
Thus, in a fuel cell, when there is a hydrogen leak caused by damage to the membrane and the like, it is necessary that this be discovered early.
Thus, conventionally, for example, in Japanese Unexamined Patent Application, First Publication, No. Hei 6-223850, a method is disclosed in which a hydrogen detector is disposed in the exhaust path of the air that is discharged from the fuel cell, and if this hydrogen detector detects hydrogen, the supply of hydrogen gas to the fuel cell is stopped.
However, in the case of the conventional method described above, because of the relation between the detection sensitivity and the detection precision of the hydrogen detector, hydrogen leakage cannot be detected unless it has become rather advanced. Thus, it is difficult to detect hydrogen leakage before it has had a detrimental influence on the fuel cell. That is, damage to the fuel cell cannot be detected early.
In addition, in the conventional method, even if it is detected that the fuel cell has been damaged, it is not possible to specify the location of the cell in the fuel cell or which cell is abnormal (damaged).
Thus, it is an object of the present invention to provide an abnormality detecting method that focuses on the influence that the leakage of the reaction gases has on the cell voltage, and can detect damage to the fuel cell early.